Diagnostic medical ultrasound systems and methods using image based freehand needle guidance

ABSTRACT

A diagnostic medical ultrasound system having an integrated invasive medical device guidance system is disclosed. The guidance system obtains image slice geometry and other imaging parameters from the ultrasound system to optimize the guidance computations and visual representations of the invasive medical device and the imaged portion of the subject. Further, the ultrasound system obtains guidance data indicating the relative location, i.e. position and/or orientation of the invasive medical device relative to the transducer and imaging plane to optimize the imaging plane and ultrasound beam characteristics to automatically optimally image both the imaged portion of the subject and the invasive medical device.

BACKGROUND

Medical device guidance systems are used in medical applications for thepurpose of guiding various types of invasive medical devices, such asaspiration and biopsy needles, endoscopes, etc., towards specifictargets within a patient's body. These guidance systems simplify suchprocedures and make them safer and quicker to perform. In one example ofguiding a biopsy needle using a free-hand method, a position sensor isaffixed to the needle allowing the needle's absolute position in spaceto be determined. The region of the body in which the biopsy is to takeplace is imaged by an imaging system, such as ultrasound, CT or MRI. Theabsolute position of the imaging plane displayed by the imaging systemis similarly determined using a position sensor affixed to the imagingapparatus and location techniques similar to that used for the needle.With the position information of the needle and of the imaging plane,the relative position of the needle with respect to the displayedimaging plane can be determined. From the relative position information,the projected or actual needle path is computed and is superimposed inreal time on the displayed diagnostic image of the patient. This enablesthe physician to visualize the projected needle path and plan the biopsyprocedure even before the needle is inserted into the body.

The following references relate to needle guidance systems: U.S. Pat.No. 5,647,373 to Paltieli, entitled “Articulated Needle Guide ForUltrasound Imaging and Method of Using Same”; PCT Application No. WO99/27837 to Paltieli et al, entitled “System and Method For Guiding theMovements of a Device to a Target Particularly For MedicalApplications”; and U.S. Pat. No. 6,216,029 to Paltieli, entitled“Free-Hand Aiming of a Needle Guide”. An exemplary device which permitsthis type of free hand biopsy procedure is the Ultraguide 1000™ Systemmanufactured by Ultraguide, Inc., located in Denver Colo. The Ultraguide1000™ connects to an existing ultrasound system and provides a separatedisplay device which superimposes graphical representations of theactual and projected needle trajectories over the ultrasound image.

While such devices provide a valuable diagnostic tool to physicians,they also suffer from inherent inaccuracies and may make invasiveprocedures of small or odd shaped targets at minimum difficult, if notimpossible, to complete.

SUMMARY

The present invention is defined by the following claims, and nothing inthis section should be taken as a limitation on those claims. By way ofintroduction, the preferred embodiments described below relate to adiagnostic medical ultrasound system. The system includes an invasivemedical device and an ultrasound transducer operative to image a portionof a subject, the portion including a target for the invasive medicaldevice. Further, the system includes a location calculator incommunication with the ultrasound transducer and the invasive medicaldevice and operative to determine the relative location of the invasivemedical device and the ultrasound transducer. In addition, the systemincludes an image processor in communication with a display, theultrasound transducer and the location calculator and operative tocompute a first trajectory of the invasive medical device within theportion.

The preferred embodiments further relate to a method of displaying aprojected and an actual trajectory of an invasive medical devicerelative to and within a portion of a subject for use in a diagnosticmedical ultrasound system. In one embodiment, the method includesgenerating an image of the portion utilizing an ultrasound transducer,obtaining location information about the ultrasound transducer and theinvasive medical device, computing a first trajectory of the invasivemedical device relative to the portion utilizing the locationinformation, and computing a second trajectory of the invasive medicaldevice within the portion utilizing the location information.

Further aspects and advantages of the invention are discussed below inconjunction with the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a block diagram of one embodiment of a diagnostic medicalultrasound system according to the present invention.

FIG. 2A depicts a representation of an invasive procedure for use withthe embodiment of FIG. 1.

FIG. 2B depicts a representation of a diagnostic medical ultrasounddisplay corresponding to the procedure of FIG. 2A.

FIG. 3 depicts a representation of an invasive procedure in which theultrasound beam is modified according to a second embodiment.

FIG. 4A depicts a representation of an invasive procedure and ultrasonicbeam profile in the presence of a biopsy device and target.

FIG. 4B depicts a representation of an invasive procedure and ultrasonicbeam profile as modified by a third embodiment.

FIG. 5A depicts a representation of an invasive procedure andinterleaved ultrasonic beam profile according to the third embodiment.

FIG. 5B depicts a representation of a diagnostic medical ultrasoundimage of the invasive procedure of FIG. 5A.

FIG. 6A depicts a representation of an invasive procedure showing thecorresponding beam profile of the ultrasound device according to afourth embodiment.

FIG. 6B depicts a graphical representation of a diagnostic medicalultrasound image corresponding to the invasive procedure of FIG. 6Aaccording to the fourth embodiment.

FIG. 7A depicts a representation of an invasive procedure using anultrasound device capable of modifying the ultrasonic beam profileaccording to the fourth embodiment.

FIG. 7B depicts a graphical representation of a diagnostic medicalultrasound image corresponding to the procedure of FIG. 7A according tothe fourth embodiment.

FIG. 8A depicts a representation of an invasive procedure according to afifth embodiment showing the ultrasonic beam profile in a firstorientation.

FIG. 8B depicts a graphical representation of a diagnostic medicalultrasound image corresponding to the beam profile shown in FIG. 8Aaccording to the fifth embodiment.

FIG. 9A depicts a second representation of the invasive procedure ofFIG. 8A showing an ultrasonic beam profile orthogonal to the beamprofile depicted in FIG. 8A, according to the fifth embodiment.

FIG. 9B depicts a graphical representation of a diagnostic medicalultrasound image corresponding to the beam profile shown in FIG. 9A,according to the fifth embodiment.

FIG. 10 depicts a representation of an invasive procedure using anultrasound device with interleaved beam profiles orthogonal inorientation, according to a sixth embodiment.

FIGS. 11A and 11B depict a graphical representation of a side by sidediagnostic medical ultrasound images corresponding to the procedure ofFIG. 10 produced by the beam profiles depicted in FIG. 10, according tothe sixth embodiment.

FIG. 12 depicts a graphical representation of an invasive procedureusing a 2D array ultrasound device with a corresponding imaging plane,according to a seventh embodiment.

FIG. 13 depicts a graphical representation of the invasive procedure ofFIG. 12 using a 2D array diagnostic ultrasound device depicting thecalculated position and orientation of a new imaging plane according tothe seventh embodiment.

FIG. 14 depicts a graphical representation of the invasive procedure ofFIG. 12 using a 2D array diagnostic ultrasound device, depicting themodified position and orientation of the imaging plane according to theseventh embodiment.

FIGS. 15A-C depicts a graphical representation of diagnostic medicalultrasound image plane displays according to the seventh embodiment.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

In one known embodiment of an invasive medical device guidance system,the system is separate from the medical imaging system, such as adiagnostic medical ultrasound system, which is used to display thetarget. The guidance system connects to the imaging system, such as viaa video output port, and utilizes the images generated by the imagingsystem to create further representations showing actual and projecteddevice guidance information. To create these representations of thetrajectory of the invasive medical device, such as a needle, to a targetinside the patient's body, the guidance system superimposes a graphicalrepresentation of the actual and/or projected trajectory of the deviceover the externally supplied ultrasound images. The trajectories, actualor projected, are computed from known position information determined bysensors on the medical device and on the ultrasound transducer.Alternatively, other methods known in the art can be used to determinethe position information. This allows the guidance system to merge thetwo dimensional ultrasound images obtained from the ultrasound systemwith a graphically represented image of the needle trajectory anddisplay this merged image to the physician or sonographer.

One problem with such systems, especially where diagnostic ultrasound isutilized as the medical imaging system, is that the area of the bodyimaged by the ultrasound transducer is not, strictly speaking, a flatplane as shown on the display and provided to the external guidancesystem as described above. An ultrasound transducer images a slicethrough the body having a width, depth and thickness (typicallydescribed using the azimuth, range and elevation dimensions,respectively). These dimensions are a function of the transducerconstruction and ultrasound beam formation and are largely dependent onthe desired focal point to be achieved for imaging a particular portionof a subject. The construction of an ultrasound transducer and beamformer, in the case of a transducer with a fixed elevation, or elevationconfiguration settings, in the case of a transducer with an activeelevation, must consider the best slice thickness for a particularclinical application such as imaging the abdomen vs. a thyroid gland. Inthe case of the abdominal transducer, the elevation plane will normallybe thicker and usually focused deeper because the targeted abdominalcontents are larger and more difficult to penetrate. A thicker and moredeeply focused slice improves the ability of the transducer to transmitlarger amounts of ultrasound energy into the body therefore improvingthe amount of returned energy for processing. This is in contrast to thethyroid gland which is considerably more superficial and smaller in sizethereby allowing a thinner and shallower elevation focus to be utilized.In general it is always desired to have as thin a slice profile aspossible, yet maintaining an acceptable level of penetration of thedesired anatomy. As the penetration needs are increased, the ultrasoundslice tends to thicken therefore increasing the amount of volumeinsonated. Using known algorithms, such as volume averaging, the imageprocessor of the ultrasound system essentially flattens the returnedultrasound data in the elevation dimension when the image is ultimatelyrendered as a two-dimensional representation on a video display or otheroutput device. This may lead to some distortion of the structures beingimaged or create slice artifacts which decrease the clarity of theimage. As the elevation thickness grows to meet a clinical application'sneeds, the ambiguity in the displayed image when attempting to determinethe location of a structure is increased.

A guidance system which fails to take into account this slice geometrywill similarly misrepresent, i.e. render inaccurate/ambiguousrepresentations of, the actual or projected intersections of theinvasive medical devices with the other structures imaged in the imagingplane. This is especially apparent for very small targets, oddly shapedtargets, or targets surrounded by critical tissue or organs. In thesecases, the elevation resolution of the ultrasound transducer, a functionof the slice thickness, is a factor in accurately guiding the invasivemedical device. The inability to optimize the needle guidance to accountfor slice geometry and other ultrasound parameters reduces theclinician's ability to successfully complete an ultrasound image guidedprocedure due to a more limited ability to visualize the invasivedevice.

Another problem with non-integrated imaging and guidance systems isthat, often, the image plane or scan area of the imaging system, such asan ultrasound system, is generated at a sub-optimal imaging angle tosaid invasive medical device, generated out of plane with the invasivedevice, or otherwise generated in a less than optimal fashion, whichprevents optimal imaging of both the target and the invasive devicesimultaneously. It will be appreciated that invasive devices are morevisible when they lie within the imaging plane/scan area, i.e. along theazimuth direction, and perpendicular to the emitted acoustic signals,i.e. perpendicular to the range direction, of an ultrasound transducer.In some cases, it may be impossible, due to the location of the target,to image both the target and the invasive device in a single imagingplane/scan area. This requires the clinician to reposition either theultrasound transducer, the invasive device or both in order to bestvisualize the target and/or the invasive device. While the guidancesystem typically provides feedback via the user interface to allow theclinician to optimize this positioning, the need to reposition theequipment is still a tedious and time consuming task. In addition, whereboth the target and the invasive device cannot be imaged in the sameplane/scan area, the clinician may be forced to constantly repositionthe transducer and/or invasive device to achieve an acceptable view ofthe procedure. Further, the clinician may settle for sub-optimalpositioning, and therefore viewing, so as not to waste too much time ormake the subject too uncomfortable to complete the actual procedure in atimely fashion.

FIG. 1, shows one embodiment of an ultrasound system 100 including anintegrated invasive medical device guidance system. It will beappreciated that one or more of the described components may be combinedas a single component and that one or more of the components may beimplemented completely in hardware, software or a combination thereof.Computation and rendering of the actual and projected devicetrajectories is performed using image and image slice geometry dataacquired as a function of the transducer. The actual trajectory is thetrajectory that the device is currently taking, accounting for itscurrent location (position and orientation). The projected trajectory iscomputed as the trajectory the device will take if it maintains itscurrent orientation while being advanced or retarded in position. Thispermits image data and slice geometry to be acquired and factored intothe guidance calculations. Such low level image and slice data includesthe geometric attributes of the image slice such as the slice thickness,the frequency, the dimensions of the scanned plane, the scanning formatand calibration data. Further, guidance calculations indicating theposition and/or orientation of the invasive device and transducer arefed back to the system controller to automatically optimize the imageplane for optimal viewing.

The ultrasound system 100 of FIG. 1 includes a transmit beamformer 102,an ultrasonic imaging probe or transducer 104, a receive beamformer 106,a filter block 108, a signal processor 110, a scan converter 112, animage data storage 114, an image processor 116 and a display 118.Alternatively, as described below, other types of transmitters and/orreceivers may be used. The exemplary ultrasound system 100 isconfigurable to acquire information corresponding to a plurality oftwo-dimensional representations or image planes of a subject forthree-dimensional reconstruction. Other systems, such as those foracquiring data with a two dimensional, 1.5 dimensional or single elementtransducer array, may be used. To generate each of the plurality oftwo-dimensional representations of the subject during an imagingsession, the ultrasound system 100 is configured to transmit, receiveand process during a plurality of transmit events. Each transmit eventcorresponds to firing acoustic energy along one or more ultrasound scanlines in the subject.

The transmit beamformer 102 is of a construction known in the art, suchas a digital or analog based beamformer capable of generating signals atdifferent frequencies. The transmit beamformer 102 generates one or moreexcitation signals. Each excitation signal has an associated centerfrequency. As used herein, the center frequency represents the frequencyin a band of frequencies approximately corresponding to the center ofthe amplitude distribution. Preferably, the center frequency of theexcitation signals is within the 1 to 15 MHz range and accounts for thefrequency response of the transducer 104. The excitation signals havenon-zero bandwidth.

It will be appreciated that alternative methods of generating andcontrolling ultrasonic energy as well as receiving and interpretingechoes received therefrom for the purpose of diagnostic imaging, now orlater developed, may also be used with the disclosed embodiments inaddition to or in substitution of current beam-forming technologies.Such technologies include technologies which use transmitters and/orreceivers which eliminate the need to transmit ultrasonic energy intothe subject along focused beam lines, thereby eliminating the need for atransmit beamformer, and may permit beam forming to be performed by postprocessing the received echoes. Such post-processing may be performed bya receive beamformer or by digital or analog signal processingtechniques performed on the received echo data. For example, pleaserefer to

U.S. patent application Ser. No. 09/518,972, entitled “METHODS ANDAPPARATUS FOR FORMING MEDICAL ULTRASOUND IMAGES,” now U.S. Pat. No.6,309,356, and U.S. patent application Ser. No. 09/839,890, entitled“METHODS AND APPARATUS FOR FORMING MEDICAL ULTRASOUND IMAGES,” now U.S.Pat. No. 6,551,246, the disclosures of which are herein incorporated byreference.

Upon the firing of one or more ultrasound scan lines into the subject,some of the acoustical energy is reflected back to the transducer 104.In addition to receiving signals at the fundamental frequency (i.e., thesame frequency as that transmitted), the non-linear characteristics oftissue or optional contrast agents also produce responses at harmonicfrequencies. Harmonic frequencies are frequencies associated withnon-linear propagation or scattering of transmit signals. As usedherein, harmonic includes subharmonics and fractional harmonics as wellas second, third, fourth, and other higher harmonics. Fundamentalfrequencies are frequencies corresponding to linear propagation andscattering of the transmit signals of the first harmonic. Non-linearpropagation or scattering corresponds to shifting energy associated witha frequency or frequencies to another frequency or frequencies. Theharmonic frequency band may overlap the fundamental frequency band.

The filter block 108 passes information associated with a desiredfrequency band, such as the fundamental band using fundamental bandfilter 138 or a harmonic frequency band using the harmonic band filter136. The filter block 108 may be included as part of the receivebeamformer 106. Furthermore, the fundamental band filter 138 and theharmonic band filter 136 preferably comprise one filter that isprogrammable to pass different frequency bands, such as the fundamental,second or third harmonic bands. For example, the filter block 108demodulates the summed signals to baseband. The demodulation frequencyis selected in response to the fundamental center frequency or anotherfrequency, such as a second harmonic center frequency. For example, thetransmitted ultrasonic waveforms are transmitted at a 2 MHz centerfrequency. The summed signals are then demodulated by shifting by eitherthe fundamental 2 MHz or the second harmonic 4 MHz center frequencies tobaseband (the demodulation frequency). Other center frequencies may beused. Signals associated with frequencies other than near baseband areremoved by low pass filtering. As an alternative or in addition todemodulation, the filter block 108 provides band pass filtering. Thesignals are demodulated to an intermediate frequency (IF)( e.g. 2 MHz)or not demodulated and a band pass filter is used. Thus, signalsassociated with frequencies other than a range of frequencies centeredaround the desired frequency or an intermediate frequency (IF) arefiltered from the summed signals. The demodulated or filtered signal ispassed to the signal processor 110 as the complex I and Q signal, butother types of signals, such as real value signals, may be passed.

By selectively filtering which frequencies are received and processed,the ultrasound system 100 produces images with varying characteristics.In tissue harmonic imaging, no additional contrast agent is added to thetarget, and only the nonlinear characteristics of the tissue are reliedon to create the ultrasonic image. Medical ultrasound imaging istypically conducted in a discrete imaging session for a given subject ata given time. For example, an imaging session can be limited to anultrasound patient examination of a specific tissue of interest over aperiod of ¼ to 1 hour, though other durations are possible. In thiscase, no contrast agent is introduced into the tissue at any time duringthe imaging session.

Tissue harmonic images provide a particularly high spatial resolutionand often possess improved contrast resolution characteristics. Inparticular, there is often less clutter in the near field. Additionally,because the transmit beam is generated using the fundamental frequency,the transmit beam profile is less distorted by a specific level oftissue-related phase aberration than a profile of a transmit beam formedusing signals transmitted directly at the second harmonic.

The harmonic imaging technique described above can be used for bothtissue and contrast agent harmonic imaging. In contrast agent harmonicimaging, any one of a number of well known nonlinear ultrasound contrastagents, such as micro-spheres or the Optison™ agent by Nycomed-Amershamof Norway, are added to the target or subject in order to enhance thenon-linear response of the tissue or fluid. The contrast agents radiateultrasonic energy at harmonics of an insonifying energy at fundamentalfrequencies.

The signal processor 110 comprises one or more processors for generatingtwo-dimensional Doppler or B-mode information. For example, a B-modeimage, a color Doppler velocity image (CDV), a color Doppler energyimage (CDE), a Doppler Tissue image (DTI), a Color Doppler Varianceimage, or combinations thereof may be selected by a user. The signalprocessor 110 detects the appropriate information for the selectedimage. Preferably, the signal processor 110 comprises a Dopplerprocessor 146 and a B-mode processor 148. Each of these processors ispreferably a digital signal processor and operates as known in the artto detect information. As known in the art, the Doppler processor 146estimates velocity, variance of velocity and energy from the I and Qsignals. As known in the art, the B-mode processor 148 generatesinformation representing the intensity of the echo signal associatedwith the I and Q signals.

The information generated by the signal processor 110 is provided to thescan converter 112. Alternatively, the scan converter 112 includesdetection steps as known in the art and described in U.S. Pat. No.5,793,701 entitled “METHOD AND APPARATUS FOR COHERENT IMAGE FORMATION”,assigned to the assignee of the present invention, the disclosure ofwhich is herein incorporated by reference. The scan converter 112 is ofa construction known in the art for arranging the output of the signalprocessor 110 into two-dimensional representations or frames of imagedata. The scan converter 112 converts acoustic ultrasound line data,typically in a polar coordinate system, into data which may be plottedon a Cartesian grid. Using volume averaging or other similar algorithmson the returned echo data, the slice information is merged into a single2D plane. This permits display of the ultrasound image on atwo-dimensional output device such as a display monitor. Preferably, thescan converter 112 outputs formatted video image data frames, using aformat such as the DICOM Medical industry image standard format or aTIFF format. Thus, the plurality of two-dimensional representations aregenerated. Each of the representations corresponds to a receive centerfrequency, such as a second harmonic center frequency, a type ofimaging, such as B-mode, and positional information. The harmonic basedrepresentations may have better resolution and less clutter thanfundamental images. By suppressing the harmonic content of theexcitation signal, the benefits of harmonic imaging of tissue may beincreased.

The system 100 further includes a first sensor 130 coupled with theultrasound imaging probe 104, a user interface 120, a system controller122, a second sensor 134 coupled with an invasive medical device 132, alocation (position and/or orientation) calculator 126, a needle targetbuffer 128, and an image slice calculator 124. Herein, the phrase“coupled with” is defined to mean directly connected to or indirectlyconnected through one or more intermediate components. Such intermediatecomponents may include both hardware and software based components.Further, as used herein, the term “location” is used to refer to anobject's spatial position, orientation or both. Generally, an object'sposition is a representation of the area or volume that it occupies inabsolute or relative relation to a known origin or reference or within aknown coordinate system, e.g. linear distance from the patient. Anobject's orientation is a representation of its arrangement/alignment inspace within its position in absolute or relative relation to a knownorigin or reference, e.g. angle relative to the floor. It will beappreciated that there may be many ways to define an objects location(position and/or orientation) within a given space. The image processor116 further includes a graphics drawing tool 140, a screen graphicscalculator 142 and a 3D graphics calculator 144.

The user interface 120 includes an input device which theclinician/sonographer/physician uses to interface with the ultrasoundsystem 100, including the needle guidance system. The user interface 120includes input devices such as a keyboard, mouse, trackball, touchscreen or other input devices or combinations thereof as are known inthe art. Further the user interface 120 may also include graphic userinterface (“GUI”) elements coupled with the input devices and with thedisplay 118 for both input and output functions. In addition tocontrolling the ultrasound functions of the ultrasound system 100, theuser interface 120 supplies the user with control functions foroperation and calibration of the needle guidance functionality. Forexample, the clinician may use the ultrasound system for manyexaminations that do not require an invasive device 132, therefore, theuser interface 120 would allow the clinician to activate or deactivatethe needle guidance and visualization system as needed. Additionally,controls are provided by the user interface 120 for calibration of thesubsystems included in the needle guidance and visualization system.Also, the user interface 120 may afford the user the opportunity tomodify graphical representations, imaging planes and displays producedby the ultrasound system 100 to enhance the operation of the needleguidance and visualization subsystems. Finally, the user interface 120allows the user to coordinate multiple ultrasound probes 104 eachcoupled with its own sensor 130, and/or multiple invasive devices 132,each coupled with its own sensor 134 for complex guidance procedures.

The system controller 122 controls and coordinates the functions of theultrasound and guidance subsystems. In one embodiment, the systemcontroller includes The term “system controller” broadly refers to theappropriate hardware and/or software components of the ultrasound system100 that can be used to implement the preferred embodiments describedherein. It should be understood that any appropriate hardware (analog ordigital) or software can be used and that the embodiments describedherein can be implemented exclusively with hardware. Further, the systemcontroller 122 can be separate from or combined with (in whole or inpart) other processors of the ultrasound system 100 (including attendantprocessors), which are not shown in FIG. 1 for simplicity.

The various elements of the ultrasound system including the transmitbeamformer 102, the receive beamformer 106, harmonic filter 136,fundamental filter 138, image analysis processor & display controller116, Doppler processor 146, B-mode processor 148, user interface 120,and scan converter 112 are controlled in real time by the systemcontroller 122. The controller 122 controls the operation of thecomponents of the system 100. A user, via the user interface 120, canadjust imaging parameters such as, but not limited to, image depth,image width, and frame rate. The controller 122 interprets the set-upinformation entered by the user and configures the components of thesystem 100 accordingly. An exemplary commercially available ultrasonicimaging system for use with the disclosed embodiments is the Sequoia 512system manufactured by Acuson Corporation of Mountain View, Calif.

In the disclosed embodiments, the image slice calculator 124, needletarget buffer 128, location (position and/or orientation) calculator 126are also coupled with the controller 122 such that the relative orabsolute position and/or orientation of the transducer 104 and invasivedevice(s) 132 is now accessible to the ultrasound system 100 asdescribed herein.

Location sensors 130, 134 are sensors capable of sensing location, i.e.position, orientation or both parameters and generating datarepresenting the location, i.e. position, orientation, or both, of thesensor 130, 134 and whatever the sensor 130, 134 is attached to, i.e.the probe 104 or invasive device 132. More than one sensor 130, 134 maybe provided wherein one sensor 130, 134 senses position while the othersenses orientation. The sensor 130 may be internal or external to theprobe 104.

In one embodiment, the probe 104 includes an ultrasonic imagingtransducer array with the capability, either mechanically orelectronically, of beam steering in the azimuth, elevation or bothdimensions, elevation beam focusing or combinations thereof. The arraymay have an active or fixed elevation geometry. An active elevationgeometry permits both beam steering and elevation focusing. Elevationbeam focusing differs from beam steering typically by the amount ofactive independent channels (and piezoelectric elements) devoted to beamformation; focusing is a subset of beam steering. When one speaks of a“2D array”, the transducer is beam steerable in elevation while atransducer with active elevation may not be beam steerable but iscapable of focusing in elevation.

The invasive medical device or implement 132 may be a needle, cannula,catheter, probe or other type of invasive device including biopsydevices. The device 132 is fitted with one or more location sensors 134.The device may be further fitted with sensors which detect deformation,such as strain gauges or other force sensors. An exemplary device whichdetects such deformation is a colonoscope as described in U.S. Pat. No.5,728,044 to Shan, the disclosure of which is herein incorporated byreference.

The location sensors 130, 134 may be attached to the transducer 104 orinvasive device 132 or may be integral. Further, the sensors 130, 134may operate by optical, magnetic, gyroscopic, accelerometric or othermeans or any combination thereof. In addition, the sensors 130, 134 maybe wired or wireless, active or passive. Exemplary medical devicelocation systems are described in more detail in U.S. Pat. No. 5,529,070to Augustine et al and in commonly assigned U.S. Pat. No. 6,122,538,entitled “MOTION MONITORING METHOD AND SYSTEM FOR MEDICAL DEVICES” toSliwa et al, the disclosures of which are herein incorporated byreference.

The location calculator 126 determines the absolute and/or relativeposition and/or orientation of the transducer 104 and the invasivemedical device 132. In one embodiment, the location calculator 126computes position only, such as when using a flexible catheter whereonly the position of the catheter tip need be known. In anotherembodiment, the location calculator 126 determines both position andorientation, such as for a rigid invasive device 132 where the angle ofthe device 132 must be determined. Alternatively, the locationcalculator 126 can determine the position and/or orientation of multipletransducers 104, multiple invasive medical devices 132 or combinationsthereof. The output of the location calculator 126 is sent to the needletarget buffer 128 and the 3D graphics calculator 144.

The 3D graphics calculator 144 computes the projected and actualtrajectories of the invasive medical device(s) 132 and the intersectionof the device(s) 132 with the portion of the subject represented by theultrasonic image. Three-dimensional (X, Y, Z) axis data is maintainedfor this calculation. The 3D graphics calculator 144 receives inputsfrom the location calculator 126, the needle target buffer 128 and theimage slice calculator 124. The output of the 3D graphics calculator 144goes to the screen graphics calculator 142 which coverts the trajectorydata to graphical representations that can be super imposed on theimage/display 118. The output of the 3D graphics calculator 144 alsogoes to the system controller 122 and may be used to align the imagingtransducer's 104 scan area, elevation profile and/or beam orientationfor optimal visualization of the invasive medical device(s) 132.Alternatively, the output of the location calculator 126 may be used bythe system controller 122 for re-orienting the image plane as will bedescribed below. This alignment may be under the clinician's control ormay be automatically performed to optimize the visualization of thedevice 132 and the target for the given procedure.

The image slice calculator 124 receives information from the systemcontroller 122 about the imaging attributes of the transducer or thoseattributes being used or changed by the sonographer via the userinterface 120. This attribute information is used by the image slicecalculator 124 to take into account changing image slice characteristicsdue to, but not limited to, frequency, transmit focus location, scanarea and the subsequent effect of these variables on the image slicegeometry. In one embodiment of the invention, the slice thickness may beacquired from calibration or reference data stored in the slicethickness calculator. This calibration/reference data may be determinedfrom pre-acquired measurement data that has been loaded as part of theimaging control/configuration data when a transducer is activated. Themeasurement data may be generated in several ways including theoreticalor water tank analysis of the elevational pressure profile. The imageslice calculator 124 determines the slice thickness of the current imageby utilizing the controller information, including beam formationparameters, the user interface 120 settings, and the slice referencedata. The image slice calculation data is sent to the image processor116 for integration of the position and/or orientation information forthe 3D graphics calculation of the device 132 trajectory and the sliceorientation.

The needle target buffer 128 receives input from the location calculator126 and the user interface 120 via the system controller 122. The needletarget buffer 128 enables the system 100 to graphically display the areaof the subject, via the ultrasound image, into which the invasivedevice(s) 132 will be placed. The needle target buffer 128 computes thelocation of transducer 104, the imaging plane produced therefrom and theinvasive device 132 and generates image data which can be merged withthe displayed ultrasound image. The needle target buffer 128 factors inposition and/or orientation accuracy and device 132 deformation. Theneedle target buffer 128 stores reference data regarding the tolerancesand/or error in the position and/or orientation data returned by thelocation sensors 130, 134 and also the potential deflection of theinvasive device 132 being used. Since there may be error in the accuracyof the location sensors 130, 134 or potential deflection of the invasivedevice 132, it is important to convey this error in the graphicaldisplay of the needle trajectory to the clinician performing the biopsy.This error potential is computed by the needle target buffer 128 and, inone embodiment, may be graphically represented to the clinician bydemarcated regions of confidence of where the invasive device 132 willtrack as it is advanced. This graphical representation may be indicatedby discrete lines and/or dots, or areas of shading or color representingthe predicted confidence of the invasive device 132 location.

The screen graphics calculator 142 converts the 3D orientation and imageplane intersection information into parameters which may be displayed ona Cartesian coordinate system. Scan area and screen formatting changesare communicated to the screen graphics calculator 142 via the systemcontroller 122. This permits the needle guidance image data to beintegrated with the ultrasound image data from the scan converter fordisplay on the 2D output device, such as the display monitor 118.

The graphics drawing tool 140 applies graphical attributes to the twodimensional coordinates of the invasive device(s) 132 and imaging planeintersection(s) in order to differentiate multiple invasive devices 132as well as target area attributes. This provides graphical feedback onthe display 118 so the clinician is informed of the position and/ororientation of the invasive device(s) 132 and their potential error. Inthis way, the invasive device(s) 132 may be successfully advanced to theintended target. In many cases the invasive device(s) 132 may be poorlyidentified by their ultrasonic echoes alone, due to a poor angle ofincidence to the ultrasound beam, deflection of the invasive device 132,or the construction of the invasive device 132. The graphical display,via the graphics drawing tool 140, helps the clinician direct theinvasive device(s)132 when it may not be adequately visualized.Additionally, the graphical display, using the graphics drawing too 140also gives the clinician to ability to plan the trajectory of theinvasive device(s) 132 prior to inserting it into the patient. This isbecause the predicted trajectory, in the form of a graphical display, isoverlaid onto the ultrasound image giving the clinician the opportunityto modify the transducer 104 position and/or orientation, the invasivedevice 132 position orientation or both prior to subjecting the patientto the invasive device 132 and potentially causing the patient furtherpain and discomfort.

Referring now to FIGS. 2A and 2B, there is shown an exemplary ultrasonicguided biopsy procedure and corresponding ultrasonic image. In thisfirst embodiment, the position and/or orientation computation,ultrasound image beam and slice characteristics are known to the imageanalysis processor and display controller 116, as described above.

Consider an ultrasonic image guided biopsy of the liver. The image plane202, also referred to herein as the scan area, scanned by the transducer104 is oriented manually by physical movement of the transducer by theclinician (or automatically and without transducer movement as will bedescribed below) to include the target 204 and the intended trajectoryof the invasive device 132. The position and/or orientation of theinvasive device 132 is indicated on the ultrasound image 118 by agraphic display 208 of the predicted pathway of the invasive device 132,accounting for the slice thickness. This prediction/display helps theclinician plan the angle and insertion location of the invasive device132, with consideration of the slice thickness, to accurately intersectthe intended target 204. It is important to consider the slice thicknessin the trajectory of the invasive device 132 to the target 204 becausethe invasive device 132 may bend in the elevation plane similar to theway light is refracted passing between mediums of different densities,which may not be accurately represented unless accounting for thethickness of the area through which the device 132 is passing. Inaddition, since the ultrasound transducer 104 is usually hand heldduring an invasive study, the clinician may inadvertently move theultrasound transducer solely in elevation making it possible to miss thetarget without any overt indication.

The disclosed system is capable of giving the clinician graphical cueswhich consider changes in elevation profile due to beam formation orinadvertent ultrasound transducer 104 movement. Such cues includegraphical indicators, such as lines, dots, dashes, shaded and coloredregions which indicate the deformation of the invasive device 132 as itpasses through the ultrasound image with differing elevationalthicknesses. With the disclosed embodiments, the elevation profile isknown to the needle guidance system. Therefore the clinician can referto the graphical cues generated by the guidance system to the ultrasoundimage 118 to modify the invasive device's 132 trajectory 208 orreposition the ultrasound probe 104. These graphical cues includeindicators such as lines, dots, dashes, shaded and colored regions whichindicate the predicted trajectory of the invasive device 132 and informthe clinician to the potential success of the invasive device 132reaching the intended target. Further, the clinician is able to moreclearly see the relationship between the predicted trajectory 208 asrepresented on the image 118 and the representation 210 of the target204. This type of planning is not possible with externally connectedneedle guidance systems, therefore they fail to provide the clinicianwith an insight to the difficulty or ease at which they will be able tocomplete the procedure.

Once the planning is complete, the invasive device 132 is inserted andthe actual location 206 of the leading edge of the invasive device 132is displayed within the ultrasound image 118 along with therepresentation 210 of the target 204. This invasive device 132 isindicated by a graphical display 206 in the image 118. As the ultrasoundtransducer 104 and invasive device 132 are manipulated in space, thepredicted 208 and actual trajectories 206 of the invasive device 132 areupdated in real-time, at discrete intervals, or under the control of theclinician. If the ultrasound transducer 104 strays from the predicted208 and/or actual trajectory 206 of the invasive device 132, thegraphical displays 206, 208 will deform to convey the exiting of theinvasive device 132 from the field of view. This includes anydeformation in the elevation—or slice thickness-plane.

Referring now to FIG. 3, there is shown an transducer probe 104 for usewith a second embodiment of the system 100 which improves the imaging ofthe invasive device 132 by providing the capability to steer theultrasound beam emitted by the transducer 104 without moving thetransducer 104. In this second embodiment, the position and/ororientation computation, ultrasound image beam and slice characteristicsare known to the image analysis processor and display controller 116 andalso to the system controller 122. An ultrasound image frame can beobtained in which the ultrasound beam 306 can be aligned, i.e. steered,to be more perpendicular 308 to the angle of the invasive device's 132trajectory. FIG. 3 demonstrates steering the ultrasonic beam within theazimuthal dimension of the imaging plane, maintaining an imaging planeperpendicular to the face of the transducer. Beam steering in theelevational dimension, wherein the imaging is non-perpendicular to thetransducer face, alone or in combination with azimuthal beam steering,is also contemplated and described below. One method of controlling thisbeam steering or angle gives the clinician, via the user interface 120,control of the ultrasound beam 308 angle for better acoustic reflectionof the invasive device 132. For example, a control knob, slider orjoystick may be provided to control beam angle or the beam angle may becontrolled via a displayed graphic user interface. When the ultrasoundbeam 306 is aligned more perpendicular 308 to the invasive device 132,the reflection from the invasive device 132 has a higher amplitude echoback to the transducer 104. This provides better visualization by theclinician of the invasive device 132 for monitoring and directing thetrajectory of the invasive device 132. Another method of beam alignmentcontrol utilizes known position and/or orientation information about theinvasive device 132. The position and/or orientation information iscommunicated to the system controller 122 to automatically revise thebeam angle 308 by directing the transmit beamformer 102, receivebeamformer 106, filter block 108, and signal processor 110, to modifythe ultrasound beam 308 more perpendicularly to invasive device 132.Since the angle of the invasive device 132 can vary and it's positionand/or orientation is known, the beam angle of the ultrasound image canbe updated accordingly in real time, at discrete intervals or under thecontrol of the clinician, as the invasive device 132 changes positionand/or orientation. The optimal invasive device 132 visualization beamorientation 308 may be dynamically interleaved with the conventionalultrasound beam orientation 306, optimal for visualizing the targetarea, for practical clinical imaging. Line, group of line, frame andgroup of frame interleaving may be used. This type of integratedultrasound beam modification 308 based on the position and/ororientation of the invasive device 132 allows for optimal viewing ofboth the invasive medical device 132 and the imaged portion of thesubject. Graphical displays (not shown) indicate the predicted andactual trajectories 208, 214, 206 of the invasive device 132, asdescribed.

Referring now to FIGS. 4A, 4B, 5A and 5B, there is shown an invasiveprocedure for use with a third embodiment of the ultrasound system 100with integrated needle guidance functionality. As referenced in theabove embodiments, the position and/or orientation computation,ultrasound image beam and slice characteristics are known to the imageanalysis processor and display controller 116. The ultrasound system 100further includes an ultrasound transducer 104 that is capable ofelevation focusing. Elevation focusing, as described above, permits thenarrowing of the image slice for the purpose of minimizing elevationalambiguity in the displayed image. The ultrasound slice profile and theposition and/or orientation of the invasive device 132 is also known bythe system controller 122 of the ultrasound system 100. The beamformation is controlled by the transmit and receive beamformers 102,106, under direction of system controller 122, in order to optimize theultrasound image slice profile 402, 406 for better visualization of theinvasive device 132 while minimizing elevational ambiguity. Optimizingthe image slice by reducing the elevational thickness of the image slicefurther reduces the inclusion of spurious echoes around the invasivedevice 132, therefore insuring the voxel of ultrasound data includesprimarily the reflection of the invasive device 132. This improves thecontrast in displayed intensity between the invasive device 132 and thesurrounding tissue. As described in the previous embodiments, improvedvisualization of the invasive device 132 is paramount to the cliniciansuccessfully performing an invasive ultrasound image guided procedure.Non-integrated guidance systems are unable to feed back their guidancedata to the ultrasound system to control elevation image content oroptimize the ultrasound image slice profile 406 based on the positionand/or orientation of the invasive device 132. This reduces theclinician's ability to visualize the invasive device 132, whichincreases the risk of missing the intended target 404, 408.

FIG. 4A shows the normal image slice profile 402. FIG. 4B shows theoptimized, narrower image slice profile 406. FIG. 5A shows the normal502 and optimized 504 slice profiles interleaved to provide optimizedvisualization of the invasive device 132 and the target 506. Referringto FIG. 5B, the graphical image display 118 indicates the predicted 514and actual trajectories 510 of the invasive device 132 as well as thetarget image 512. To further improve a clinician's ability to visualizethe invasive device, the beam steering capability described above andshown in FIG. 3 may be combined with the embodiments in FIGS. 4A, 4B, 5Aand 5B. The ability to align the ultrasound image 306 moreperpendicularly 308, while narrowing the beam profile 406 by using theknown position and/or orientation of the invasive device 132 furtheraugments visualization of the invasive device 132 as described.

Referring now to FIGS. 6A, 6B, 7A and 7B, there is shown a fourthembodiment utilizing a two dimensional (“2D”) transducer array 104. The2D ultrasound transducer array 104 is under system control and iscapable of re-orienting the image plane 606 and beam angle created bythe transducer 104. 2D Arrays are typically used to acquire 3D images.2D arrays can also be used to acquire 2D images. In the case ofacquiring 2D images with a 2D array, there are a number of advantages:

the frame rate can be very high because only 2D images are acquired;

the elevation slice thickness can be controlled tightly at all depthssuch that more uniform elevation resolution can be achieved as comparedto a conventional 2D image acquired using a one dimensional (1D) array;and

the image plane 606 can be arbitrarily oriented.

The fact that imaging plane 606 can be arbitrarily oriented has, itself,a number of advantages. In the aforementioned biopsy, as the clinicianadvances the invasive device 132, the position and/or orientation of theultrasound transducer 104, invasive device 132, image plane 606 as wellas the beam orientation is determined and provided to the systemcontroller 122. The clinician can mark the target 610 in the ultrasoundimage 118 with a graphical reference indicator 618 for which theposition and/or orientation is now known by the system 100 to fix thetarget location. As the clinician advances the invasive device 132, theultrasound image plane 606, beam orientation, predicted 616 and actual612 trajectory are modified in real-time, at discrete intervals or underthe control of he clinician, for accurate tracking. The ultrasound image118 is fixed relative to the marked target 610, 618 and invasive device132 even as the ultrasound transducer 104 is moved during the naturalcourse of an invasive ultrasound image guided study. Referring to FIG.7A, this is achieved by the ultrasound system 100 either automaticallyor under the control of the clinician via the user interface 120. Theultrasound system 100 aligns the image plane 704 to a plane whichincludes the predicted 714 and actual 708 trajectory of the invasivedevice 132 and the indicated target 716. This alignment of the imagingplane 704 may be achieved through beam steering in the azimuthal and/orelevational dimensions as has been described. Graphically, this is shownin FIG. 7B showing that the image of the invasive device 132 and target710 is maintained similarly as that of FIG. 6B despite movement of thetransducer 104. In this way, the clinician maintains consistentreal-time monitoring of the invasive device 132 and confirmation ofaccurate placement. As indicated previously, prior art embodiments donot access ultrasound system 100 beam formation and processinginformation, so cannot improve the success of an ultrasound image guidedbiopsy by the means described.

Referring now to FIGS. 8A, 8B, 9A and 9B, there is shown a fifthembodiment, using an aforementioned 2D or rotational array 104 (such asis used in a transesophageal transducer) where the position and/ororientation of the transducer 104, image plane 804, beam orientation,and invasive device 132 is known. As the clinician advances the biopsydevice 132 the display 118 indicates the predicted 814 and actual 808trajectory overlaid over the ultrasound image 118 via graphical means,as described. When using this embodiment, the position and/ororientation of the ultrasound beam and invasive device 132 is known. Theclinician can indicate via user interface control whether or not toimage the needle 132 in it's longitudinal axis or to rotate the plane904 of the image, as shown in FIGS. 9A and 9B, to the short axis forvisualization of the needle 132 tip 910. This allows the clinician thefull confidence and opportunity to visualize the progress of theinvasive device 132 in two planes 804, 904 under ultrasound imageguidance which is not possible with prior art embodiments. In oneembodiment, the imaging planes are maintained perpendicular to thetransducer 104 face. In an alternate embodiment, one or both imagingplanes are also steered in the azimuthal and/or elevational dimensionsfor further optimized viewing and/or tracking of the device 132 tip 910.

Referring now to FIGS. 10, 11A and 11B, there is shown a sixthembodiment, using the aforementioned rotational 2D array where theposition and/or orientation of the ultrasound transducer 104, imageplane 1006, 1008, beam orientation, and invasive device 132 is known.The clinician can mark the position and/or orientation of the target1004 with a graphical indicator in which the position and/or orientationis marked for reference in the ultrasound image. See FIGS. 11A and 11B.As the clinician advances the invasive device 132, two imaging planes1006, 1008 are formed to image 1) the plane of the needle 132 path tothe target 1004, and 2) a plane that tracks the needle 132 tip incross-section. The needle 132 insertion to target plane 1006 is fixed toinclude the marked target 1106 and the invasive device 132. This planeremains 1006 intact even though the ultrasound transducer 104 is movedduring the course of the biopsy. The second plane 1008 is formed at anangle to the first plane's 1006 azimuth dimension. This angle ispreferably perpendicular in azimuth to the first image plane 1006. Asthe biopsy device 132 is advanced towards the target 1004, the secondplane 1008 sweeps through the body, always located at the predicted1110, 1116 and actual 1102, 1112 trajectory of the invasive device 132tip yet maintaining perpendicular placement to the first plane 1006. Thefirst 1006 and/or second 1008 planes may also be steered in theazimuthal and/or elevational dimensions for further optimal viewingand/or tracking. It is important to the clinician to identify theinvasive device 132 tip, as this is the leading edge of the invasivedevice 132 and determines accurate placement towards the intended target1004, 1106. These two frames would be displayed as separate images 118on one display on the ultrasound system 100. As in aforementionedembodiments, the predicted and actual trajectories 1102, 1112, 1104,1110, 1114, are indicated graphically in each ultrasound image 118 inFIGS. 11A and 11B. An additional display element is provided which is agraphical identification of the first plane 1006 and second planes 1008as planer orientation markers 1116, 1108 respectively. This provides theclinician with a reference of where the first plane 1006 is located inreference to the second plane 1008 and the second plane location inreference to the first plane 1006. Plane references are important to theclinician when multiple ultrasound image planes are presented on onedisplay 118. This allows one to quickly interpret two distinctlydifferent views of objects within the ultrasound image 118 givingconfidence of position and/or orientation during an ultrasound guidedinvasive procedure.

Referring now to FIGS. 12-14 and 15A, 15B and 15C, there is shown aseventh embodiment allowing the clinician to optimally view the targetand invasive medical device, as well as the projected and actualtrajectories of the invasive medical device, relative to a commonreference, such as the tip, or other portion, of the invasive medicaldevice. Consider the application of a breast biopsy using a needle 132.Referring to FIG. 12, there is shown a 2D transducer array 104 acquiringa 2D image 1202 containing a target, labeled “A”. A biopsy needle 132,labeled “BC”, needs to be inserted so that the tip, labeled “B” iseventually at the target, A. Let the center of the 2D array 104 be “O”.The plane OAB is not the same as the imaging plane 1202. The system 100can automatically detect the location of point A by analyzing theimaging plane 1202. An exemplary method of accomplishing this detectionmay include the following:

1. The user views the 2D image plane 1202 on the screen and selectspoint A using a cursor, caliper or other indicator via the userinterface 120 to designate the target location in space. The output ofthis action is the coordinates of the point A in the image plane 1202.

2. The system 100 knows the location and orientation of the image plane1202 in the 3D space because it fired ultrasonic lines on the imageplane 1202.

3. Using the location and orientation of the image plane 1202 in the 3Dspace and the 2D coordinates of the point A, the system 100 computes thelocation of the point A in the 3D space.

An active or passive position or orientation sensor can also tell thesystem the location of the tip B. The system can then steer the imagingplane 1202 such that the imaging plane 1202 is identical to the planeOAB.

This adjusted imaging plane 1302 is shown in FIG. 13. The user can nowvisualize the target A and the tip of the needle 132, B at the same timeautomatically wherever the tip and the target are in the physical space.However, the axis of the needle 132, BC, is still not visible in theimage since plane OBC is not the same as the imaging plane 1302, OAB.Knowing the location of point C (any point on the needle 132 other thanthe tip) using an active or passive position or orientation sensingmethod, the system 100 can also steer the imaging plane 1302 to theplane OBC.

This is shown in FIG. 14 as imaging plane 1402. The user can nowvisualize the needle 132, BC automatically, wherever the needle 132 isin the physical space. Note that plane OAB and OBC are not the sameplane. Therefore, in order to visualize the target A, the needle 132 tipB and the needle 132 axis BC, the system 100 acquires planes OAB and OBCin an interleaved fashion. In this way, imaging is optimized relative tothe common reference between the planes, i.e., the tip B.

FIGS. 15A-C show one possible display of these interleaved imagingplanes on the screen. FIG, 15A shows plane OAB while FIG. 15B showsplane OBC. Note that line OB is common to both planes. FIG. 1 SC shows away to present the spatial relationships of the target A, the tip B andthe needle 132, BC to the user. When the user reaches the target, A=B,i.e., as the tip of the invasive device 132 comes closer to the target,the two separate planes will converge into one plane when the tip (A)meets the target (B) in the same position and/or orientation.

In addition, invasive medical implements of the type described hereinare typically somewhat flexible in their structure. As they are insertedinto the subject, they tend to bend or deflect. This deflection willcause divergence in the projected trajectory of the implement from theactual trajectory. The projected trajectory is computed under theassumption that the invasive implement, i.e. its orientation, willremain straight and not bend as it is inserted into the body. Thedisclosed embodiments compensate for deviations in the actual trajectoryof the invasive device to properly compute the projected trajectory. Theamount of deflection is dependent upon the hardness of the medium, thehomogeneity of the medium, and the characteristics of the invasivedevice such as its thickness or gauge, the material it is fabricatedfrom and its structure. Further, the degree of deflection is alsodependent upon the clinician's insertion technique and the amount ofmanipulation imparted on the device during insertion. The disclosedembodiments can utilize invasive devices which are bendable ordeformable or rigid. Further the invasive device may have a straight,curved or other profile.

In addition, while the ultrasound slice is not altered by the invasivedevice as it enters the subject (i.e., the same portion is imaged by thetransducer whether the invasive device is present or not providing thetransducer is not moved and other settings do not change), the portionof the subject being imaged may deform as the invasive device encountersand/or passes through. In this case, the target location will bedeformed due to the Z-axis component of the slice. In one alternateembodiment, this deformation is represented on the display as anon-symmetrical trajectory line to accurately depict the slicenon-uniformity.

In still other alternative embodiments, multiple invasive devices areused substantially simultaneously, such as in laproscopic procedures. Insuch embodiments, the position and/or orientation of each device isdiscretely displayed relative to and within the imaged subject. Further,the scan area/imaging plane and/or beam characteristics, such as beamangle, may be altered in real time and interleaved so as to optimallyview the target as well as all or a sub-set of the invasive medicaldevices in use. In still other alternative embodiments multiple imagingtransducers may be utilized simultaneously, such as in intraoperative,or endocavity ultrasound imaging methodologies. In such embodiments theposition and/or orientation of each transducer is identified anddisplayed relative to and within the imaged subject.

It is therefore intended that the foregoing detailed description beregarded as illustrative rather than limiting, and that it be understoodthat it is the following claims, including all equivalents, that areintended to define the spirit and scope of this invention.

We claim:
 1. In a diagnostic medical ultrasound system, a method ofdisplaying a trajectory of an invasive medical device relative to andwithin a portion of a subject, said method comprising: (a) generating animage of said portion utilizing an ultrasound transducers saidtransducer having at least one operational characteristic; (b) obtaininglocation information about said ultrasound transducer and said invasivemedical device; (c) obtaining, automatically, said at least oneoperational characteristic of said ultrasound transducer; (d) computinga first trajectory of said invasive medical device relative to saidportion utilizing said location information and said at least oneoperational characteristic; and (e) computing a second trajectory ofsaid invasive medical device within said portion utilizing said locationinformation and said at least one operational characteristic.
 2. Themethod of claim 1, further comprising: (f) displaying said image of saidportion on a display, said image further comprising representations ofsaid first and second trajectories.
 3. The method of claim 2, whereinsaid portion is characterized by having three-dimensions and said outputdevice is characterized by having two-dimensions and further wherein (f)further comprises compensating said representations in said image forsaid displaying of said three-dimensional portion on saidtwo-dimensional output device utilizing said location information andsaid at least one operational characteristic.
 4. The method of claim 1,wherein said portion is characterized by a slice geometry and furtherwherein (d) and (e) further comprise obtaining data representing saidslice geometry and compensating for said slice geometry based on saiddata.
 5. The method of claim 4, wherein said compensating furthercomprises controlling said diagnostic medical ultrasound system toautomatically adjust said slice geometry for optimal representation ofsaid first and second trajectories.
 6. The method of claim 4, furthercomprising: (f) displaying an image of said portion on a display, saidimage further comprising representations of said first and secondtrajectories; and wherein said compensating further comprises adjustingsaid representations based on said data.
 7. The method of claim 4,wherein said compensating further comprises controlling said diagnosticmedical ultrasound system to automatically adjust an ultrasonic beamemitted by said ultrasound transducer.
 8. The method of claim 1, whereinsaid invasive medical device is characterized by deformability andfurther wherein (b) further comprises obtaining deformation informationof said invasive medical device and (d) and (e) further comprisecompensating for said deformation.
 9. The method of claim 1, whereinsaid portion further comprises a target and further wherein (d) and (e)further comprise computing guidance information to guide said invasivemedical device to said target.
 10. The method of claim 1, wherein saidimage lies in an imaging plane of said ultrasound transducer, saidmethod further comprising: (f) controlling said diagnostic medicalultrasound system to automatically align said imaging plane to optimizeimaging of said invasive medical device based on said computed first andsecond trajectories.
 11. The method of claim 10, wherein (f) furthercomprises aligning said imaging plane to be substantially at least oneof parallel and perpendicular to at least one of said first and secondtrajectories.
 12. The method of claim 10, further comprising: (g)interleaving said imaging plane optimized for imaging said invasivemedical device with an imaging plane optimized for imaging said portion.13. The method of claim 10, wherein (f) further comprises aligning saidimaging plane to a common reference between a first plane including atleast one of said first and second trajectories and a second planeincluding said portion.
 14. The method of claim 10, wherein (f) furthercomprises aligning said imaging plane in elevation non-perpendicular toa face of said ultrasound transducer.
 15. The method of claim 10,wherein (f) further comprises rotating said imaging plane about an axisperpendicular to a face of said ultrasound transducer.
 16. The method ofclaim 1, further comprising: (f) controlling said diagnostic medicalultrasound system to automatically adjust an ultrasonic beam emittedfrom said ultrasound transducer to achieve a more perpendicular incidentangle of said ultrasonic beam with said portion to said first trajectorybased on said computed first and second trajectories.
 17. In adiagnostic medical ultrasound system, a method of displaying atrajectory of an invasive medical device relative to and within aportion of a subject, said portion including a target portion of saidinvasive medical device, said method comprising: (a) generating a firstimage of said portion utilizing an ultrasound transducer, said imageincluding said target portion, said ultrasound transducer emittingultrasonic energy according to a first beam parameter, said first beamparameter optimized to image said target portion; (b) obtaining locationinformation about said ultrasound transducer and said invasive medicaldevice; (c) computing a trajectory of said invasive medical devicerelative to said portion utilizing said location information; (d)computing a second beam parameter based on said location information andsaid trajectory, said second beam parameter being optimized to imagesaid invasive device; (e) causing, automatically, said ultrasoundtransducer to emit ultrasonic energy according to said second beamparameter; and (f) generating a second image of said portion utilizingsaid ultrasound transducer, said image including a representation ofsaid invasive device.
 18. The method of claim 17 further comprising: (g)controlling, automatically, said diagnostic ultrasound system tooptimize said first and second beam parameters to optimally view bothsaid target portion and said invasive medical device.
 19. The method ofclaim 17 further comprising: (g) interleaving said first and secondimages on said display.
 20. The method of claim 17 further comprising:(g) alternating between said first and second images on said display.21. The method of claim 17, wherein said computing of said second beamparameter further comprises computing a beam angle.
 22. The method ofclaim 21, wherein said computing of said beam angle further comprisescomputing said beam angle to be substantially at least one ofperpendicular and parallel to said invasive medical device.
 23. Themethod of claim 17, wherein said computing of said second beam parameterfurther comprises computing an elevation focus.
 24. The method of claim23, wherein said computing of said elevation focus further comprisesnarrowing said elevation focus.
 25. The method of claim 17, wherein saidcomputing of said second beam parameter further comprises computing animage plane orientation.
 26. The method of claim 25, wherein saidcomputing of said image plane orientation further comprises orientatingsaid image plane to be in a plane of said invasive medical device. 27.The method of claim 26, wherein said computing of said image planeorientation further comprises orientating said image plane to be in aplane of said invasive medical device and said target portion.